th  - 1987 - 51st ENC Conference

MF47
SOLID STATE NMR STUDIES OF ISOTOPICALLY LABELED GAMICIDIN A
IN AN ORIENTED LIPID BILAYER
L.K. Nicholson*, F. Moll III, P.V. Ix)Grasso, C.A. Guy, T.A. Cross
Department of Chemistry
and
Institute of Molecular Biophysics
Florida State University, Tallahassee, FI. 32306-3006
2H and ISN isotopic labels have been incorporated into the linear
polypeptide, Gramicidin A by a variety of techniques including bio-
synthesis, chemical peptide synthesis and exchange. The labeled
Gramicidins have been incorporated into lipid bilayers where a dimer
of the polypeptide forms a monovalent cation selective channel across the
synthetic membrane. Some of the samples have been oriented such that
the channel axis is parallel with the magnetic field. The samples have
been characterized by circular dichroism, differential scanning
calorimetry and NMR.
Solid state NMR experiments are being used to elucidate an atomic
resolution image of both the dynamics and structure of the channel.
Interpretation of the high resolution spectra of oriented samples has
provided bond orientations with respect to the channel axis. Analysis
of powder patterns has provided data for the large amplitude motions
of the polypeptide backbone.